Closed cell structure and methods and apparatus for its manufacture

ABSTRACT

Cellular cushioning material is prepared by sealing an elastic substance within cells that are formed between two flexible films. When the elastic material is a gas, means may be provided to charge the cells at superatmospheric pressure to achieve full inflation of the cells and maximum efficiency of the cushioning material.

United States Patent Troy [451 May 2,1972

154] CLOSED CELL STRUCTURE AND METHODS AND APPARATUS FOR ITS MANUFACTURE[72] Inventor: Constantine T. Troy, 1330 Cleveland Avenue, Wyomissing,Pa. 18644 [22] Filed: Apr. 28, 1969 21 Appl. No.: 819,719

[52] -U.S.Cl .,l56/l45,156/147, 156/271, 156/290, 156/292, 264/96 [51]Int. Cl. ..B32b 31/02, B32b 31/00 [58] Field of Search ..156/145, 146,147, 290, 291, 156/292, 271; 264/96 [56] References Cited UNITED STATESPATENTS 2.566.533 9/1951 Poux ..156/146X 2,670.50] 3/1954 Michiels..156/145 X 3,011,930 12/1961 Dworak ..156/145 X 3,244,571 4/1966Weisman 1 56/290 X FOREIGN PATENTS OR APPLICATIONS 747,105 3/1956 GreatBritain 156/145 625,657 7/1949 Great Britain 908,579 10/1962 GreatBritain 555,696 1/1957 Italy Primary Examiner-Carl D. QuarforthAssistan! E.\'aminerE. E. Lehmann Attorney-Synnestvedt & Lechner [57]ABSTRACT Cellular cushioning material is prepared by sealing an elasticsubstance within cells that are formed between two flexible films. Whenthe elastic materialis a gas, means may be provided to charge the cellsat superatmospheric pressure to achieve full inflation of the cells andmaximum efficiency of the cushioning material.

6 Claims, 74 Drawing Figures PATENTEnmz 1912 5 6 O, l 8 9 Consfan zme T7/0 y 'ymuama rum PATENTEDmz m2 3,660,189

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CLOSED CELL STRUCTURE AND METHODS AND APPARATUS FOR ITS MANUFACTURE I Ina preferred embodiment of the invention,,the cushioning material isformed in several steps, making it possible to store or transport anuninflatedprefabricated structure that may later be inflated to completethe construction of the cushioning material at the time of intended use.

Novel apparatus is proposed for use in the method of this invention, andof particular importance is the apparatus for forming continuous linearheat seals as two superimposed sheets of film are advanced in alengthwise direction. This apparatus makes use of aheated metal tape inthe form of an endless belt that contacts and presses the moving filmstogether and advances with the film for a sufficient distance to insurethe formation of a secure bond between the films.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to cushioning material and improved methods andapparatus for making such cushioning material. More particularly, thisinvention relates to cushionhot or cold for long periods of time. As theinvention may find primary utility in making packaging materials, it isdiscussed below in this context, although it should be understood thatthis is for convenience of description and the inventionis not solimited.

2. Description of the Prior Art in packaging goods for shipment orstorage, it is frequently necessary to surround individual articles withcushioning material to maintain an article in a fixed position within apackage and to absorb impact and other forces should the package bedropped or otherwise carelessly handled. The least expensive and mostwidely used of thesecushioning materials are cellulose materials such ascrumpled newspaper, waste paper, excelsior, waste cotton, textilescraps, and the like. All of these materials suffer from thedisadvantage that they are not elastic, but, when crushed or compacted,tend to take a permanent set in a more dense form. This detracts fromthe cushioning that these packaging materials can provide sincedensification of the packaging material will increase the shock forcesthat are transmitted to the article. Further, densification will tend toreduce the cushioning volume and permit the article to shift more freelywithin the container.

In addition to these functional defects, cellulose cushioning materialshave practical disadvantages. For example, in their finely divided orshredded form, they may carry considerable dust, dirt and lint. To avoidthis, it is sometimes necessary to prepackage or wrap articles to assurethat they will arrive at their destination in a clean condition. Whenthe articles are removed from the package, the packaging materials canbe of extreme nuisance from a housekeeping standpoint.

The composition of these cellulosic packaging materials and their finelydivided or shredded form may present a very considerable fire hazard.This is particularly'true at the shipping or packaging point where alarge amount of these highly combustible materials must be stored.

The conventional packaging materials give no protection to the articlesfrom a standpoint of being impervious to gases. Thus, fumes, corrosivevapors, moisture, and the like, may be transmitted to the product beingshipped which may cause oxidation and corrosion of the article andpermit the growth of When in finely divided or shredded form,conventional packaging materials make excellent nesting places for smallanimals and, as a result, easily may become infested by rodents, insectsand other vermin.

. techniques may be used.

Due to the comparatively poor and relatively unpredictable nature of thecommon cushioning materials, it is common practice to allow aconsiderable safety factor by surrounding an article to be shipped witha liberal quantity of packaging material. This may appreciably increaseshipping costs, both by increasing the weight of the package in whichthe article is shipped and by increasing the cubage since a largershipping container is required.

, To avoid the inherent difficulties of the shredded cellulosic shippingmaterials, attempts have been made to prepare more efiicient materialsthat have more uniform and predictable properties and are cleaner,neater and safer to use. One of the more interesting of thesesubstitutes makes use of two sheets of material, such as plastic film,that .are joined to form a plurality of closed cells. A common method ofdoing this is to emboss a first sheet of material with a pattern ofdepressions, coat a second sheet with adhesive and adhere the two sheetstogether so that air is trapped in the embossed pattern and individualresilient sealed cells are formed. Alternatively, instead of using anadhesive to laminate the sheets, heat sealing Packaging or cushioningmaterial so prepared from laminates may be quite useful, but the presentmeans known in the art to form laminates on a continuous basis withindividual sealed cells are subject to certain inherent difficulties.For example, in one method known to the prior art, a first continuousweb of plastic film is passed over a series of heated rolls. After thefilm has been softened, the film is passed over a heated roll having apattern of cavities and a series of embossments is fonned by vacuumdrawing methods. A second unembossed heated web is then run against thefirst embossed web as the first web is passing over the embossingrolland the two sheets are heated sufficiently close to their melting pointto cause fusion of the films at their point of contact, thus formingindividual sealed cells. When this technique is used, the

' web of cushioning material will have one embossed side and one flatside. t

Cushioning material of this type now available on the'market isfrequently manufactured from plastic film which is itself a laminate.One lamina of the film may be selected forits low melting point and easeof fusing to the mating sheet of film,

and the other lamina may be selected'for its relatively high meltingpoint, its superior tensile strength, and its low gas and vaportransmission rate. It can readily be understood that these combinationsof properties are quite beneficial since, using the above-describedtechnique, it is desired to get a strong bond by melting and yet retainsufficient strength of the plastic films so that they can be handledwithout tearing. It is also apparent that the value of the cushioningmaterials would be destroyed if the gas transmission rate weresufficiently high to permit the cellular structure to collapse underload.

While cushioning material in the form of cellular plastic sheets avoidsmany of the difficulties encountered in the use of cellulosic typematerials, they, too, suffer from certain inherent physical inadequaciesand may present difficult problems in their manufacture. The primarydefect in the structure of these closed cell plastic laminates is thatthe air cells are sealed while the film is heated to an elevatedtemperature. After the web has cooled, the air contracts, causing thecells to shrink and lose some of their volume and firmness. Thiscondition may be visually recognized by the characteristic dimpledappearance of the cell walls of packaging material formed in thismanner. While it is perhaps unnecessary to point out that thiscontraction of the air reduces the cushioning ability of the cells, amore subtle point, somewhat a correlary to this shrinkage effect, shouldbe noted; that is, in the utilization of present production methods andapparatus, it is not possible to control the pressure within theindividual cells to be other than atmospheric. If, for example, air atsuperatmospheric pressure could be sealed within the cells, maximuminflation of the cells would be assured as well as making it possible toalter the elastic properties of the cells. By increasing the airpressure, firmer cushioning material would be provided that couldsupport heavier loads with less deforma- I struction is obtained.

tion.-Also, note that it is not possible to include a gas other than airwithin the cells using the present technology.

The cellular films known to the prior art are also inefficient in thatthey are embossed on but a single side and, at best, obtain only 50percent utilization of the plastic film. While in theory both films canbe embossed, production equipment has not yet been developed to makesuch technique practical.

The resiliency of the cushioning material may also be altered byincluding a solid elastic material, such as an elastomer within theindividual cells. This is also impractical utilizing known methods andapparatus.

In addition to the structural defects of cellular packaging material,many difficulties are inherent in its production utilizing conventionalmethods and apparatus. For example, temperature control of the variousfilms can be quite important and, in some instances, it is advantageousto maintain the embossed film at a temperature different from thebacking or flat film. In addition to requiring relatively elaboratemachinery and trained operators, an appreciable start-up time may berequired before the'operation becomes stable, thus producing scrap andmaking it economically undesirable to use the v equipment if onlyrelatively small quantities of cushioning are required. 7

It follows thatsince it is not economic to make short runs of thiscushioning material, the cushioning material must be madeat a centralmanufacturing location and then shipped to those who desire to use it;The delivered cost of the bulky cushioning material is significantlyincreased by freight rates that usually are higher for materials of lowdensity.

Lastly, it may be noted that it is impractical to add slittingto-widthand cutting-to-length devices onto machine facilities. These auxiliarydevices may require momentary shut-downs and start-ups for which thefilm-fabricating equipment is not well adapted. It can be understoodthat momentary shutdowns can destroy stable conditions as, for example,to cause a plastic film to overheat.

SUMMARY OF'TI-IE INVENTION Accordingly, it'is an object of thisinvention to provide a new and improved cushioning material and methodsand means for its manufacture. I

A further object of this invention is to provide an improved cellularstructure that may variously serve as a cushioning material, asinsulation, or as a bouyancy device.

Another object of this invention is to provide a closed cellularstructure and methods and means for its manufacture in which it ispossible to select both the gas with which the cells are filled and thepressure of the gas within the cells.

- Another object of this invention is to provide a prefabricated formthat may, when desired, be inflatedand converted into a closed cellularstructure.

Another object of this invention is to'provide apparatus for makingprefabricated forms that may readily be inflated and converted into aclosed cellular structure.

Another object of this invention is to provide methods and apparatus forinflating prefabricated forms and converting them into closed cellularstructures.

Another object of this invention is to provide a closed cellularstructure in which the cells contain a liquid or a deformable solid,such as an elastomer.

Another object of this invention is to provide a novel cushioningmaterial that may be used for packaging that is lightweight, resilient,and free from dirt and debris.

Another object of this invention is to provide novel methods andapparatus for continuously sealing superimposed laminae of heat-fusiblematerial together.

Another object of this invention is to provide cushioning material inwhich maximum utilization of the materials of con- Another object ofthis invention is to provide methods and apparatus whereby theresiliency of a closed cell cushioning material can adjustably bealtered during manufacture.

Briefly, these and other objects of this invention are achieved bysealing an elastic material, such'as a gas, within cells that are formedbetween -two flexible films. In the preferred embodiment, the films areembossed and adhered to each other along a series of spaced parallellines, then the volume between the spaced lines is inflated with anelastic material, and finally, a closed cellular structure is completedby sealing the two plastic films to each other along a second set ofspaced parallel lines that intersect with the first set of parallellines.

DEFINITIONS As used in this specification and the appended claims, thefollowing terms are given the following meanings.

Prefab refers to a partially fabricated cushioning structure made from apair of plastic films joined together along a series of parallel spacedlines'to form elongated pockets or tubes that are adapted to be inflatedwith an elastic materia and sealed into a plurality of closed cells.

Long seal" refers to a line along which two sheets of film are joined inthe direction of theirlengthwise (machine) direction.

Cross seal refers to a line along which two sheets of film are joined inthe direction of their-widthwise (cross machine) direction.

Marginal seal? refers to a long seal that joins the margins of twosheets of film.

Long channel" refers to the interstitial space between two long seals.

Cross channel refers to the interstitial'space between two cross seals.1

Near side refers to that side of the equipment visible in frontelevation, and far side" refers to the opposite side of the equipment.

Rubber refers to heat-resistant elastomers such as silicone rubbers.

Air cell cushioning refers to closed cellular materials that may containair or other gases within the cells.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of the preferredform of apparatus cross sealing with bar chain assemblies and embossing.

FIG. 2 is a section on line 22 in FIG. 1.

FIG. 3 is a front elevation and FIG. 4 a left side elevation of part ofthe margin sealing equipment shown in FIG. 1.

FIG. 5 is a front elevation and FIG. 6 a left side elevation of anotherpossible construction for making margin seals.

FIG. 7 is a front elevation, partially broken away, of an end of one ofthe bars in the upper bar chain assembly of FIG. 1, shown in its returnpath. Y

FIG. 8 is a partial left elevation and FIG. 9 a plan, partially brokenaway, of the end of the bar shown in FIG. 7.

FIG. 10 is a partial end elevation of one of the bars in the lowerbar-chain assembly in FIG. 1.

FIG. 11 is a perspective view showing how a contact plate on the barpictured in FIG. 9 slides over a stationary contact brush.

FIG. 12 is a schematic wiring diagram of the apparatus shown in FIG. 1.i

FIG. 13 is a plan of two film sheets with margin seals, cross seals andcross channels made by the apparatus shown in FIG.

FIG. 21 shows the disc attached to a heating roll shown in FIG. 18.

FIG. 22 is a partial section on line 22-22 in FIG. 2 showing details ofthe embossing rolls.

FIG. 23 is an enlarged partial section on line 23-23 in FIG. 1 showingother details of the embossing rolls.

FIG. 24 is a perspective view of part of the female embossing roll.

FIG. 25 is a plan and FIG. 26 a front elevation, partially broken away,of part of the near side of a finished prefab in its preferred form.

' FIG. 27 is an end elevation of an alternate embossing constructionusing a vacuum to emboss a pair of film sheets passing through theequipment.

FIG. 28 is a partial plan of the construction shown in FIG. 27 with thefilm sheets omitted.

FIG. 29 is a small partial section and FIG. 30 a large partial sectionon line 29-29 in FIG. 28.

FIG. 31 is an end elevation of a preferred form of equipment forconverting a prefab into air cell cushioning by inflating the cells andmaking long seals between them.

FIG. 32 is a view, partially in section, on line 32-32 in FIG. 31.

FIG. 33 is a partial section on line 33-33 in FIG. 32.

FIG. 34 is a detail, in plan, of a pipe used in the construction of FIG.31. I

FIG. 35is a partial section on line 35-35 in FIG. 31.

FIG. 36 is a section of one type of tape strand used for mak ing longseals.

FIG. 37 is an end elevation, partially in section, of equipment forinflating a prefab made without margin seals.

FIG. 38 is a plan ofa portion of FIG. 37.

FIG. 39 is a section on line 3939 in FIG. 37.

FIG. 40 shows an optional construction for heating tape strands used formaking long seals.

FIG. 41 is a detailed partial section on line 41-41 in FIG. 40.

FIG. 42 is an end elevation of a first alternate construction for makinglong seals, the sheets of film traveling over a cylinder and heat beingapplied by tape strands above and below the film sheets.

FIG. 43 is a partial section on line 43-43 in FIG. 42.

FIG. 44 is a front elevation of a second alternate construction formaking long seals, the sheets of film traveling in a straight line.

FIG. 45 isa section on line 45-45 in FIG. 44.

FIG. 46 is an end elevation of a third alternate construction for makinglong seals using heated wheel rims, the film sheets traveling over acylinder.

FIG. 47 schematically illustrates an alternate construction for making aprefab. This uses, in sequence, embossing and cross sealing withbar-chain assemblies.

FIG. 48 is a sectional detail showing how the bars in the lowerbar-chain assembly of FIG. 1 are modified for use with the constructionof FIG. 47.

FIG. 49 schematically illustrates an alternate construction for makingair cell cushioning. This uses, in sequence, embossing, long sealing andcross sealing with bar-chain assemblies.

FIG. 50 is a partial section showing modifications of the bars in theupper and lower bar-chain assemblies of FIG. 1 to adapt them to theconstruction of FIG. 49.

FIG. 51 shows a construction for making a prefab suitable forfabricating into air cell cushioning by bunch folding.

FIG. 52 schematically illustrates a construction for converting theprefab mentioned directly above into air cell cushioning by bunchfolding.

FIG. 53 is a plan view of a portion of the prefab made by theconstruction of FIG. 51.

FIG. 54 is an elevation and FIG. 55 a plan of an air cell in thecushioning made by the construction shown in FIG. 52.

FIG/56 is a front elevation, partially in section, of a construction formaking either an air cell cushioning or an elastomer-filled cushioning.This uses, in sequence, long sealing and cross sealing with bunchfolding.

FIG. 57 is a plan view, partially broken away, taken along line 57-57 inFIG. 56.

FIG. 58 is a partial section on line 58-58 and FIG. 59 a partial sectionon line 59-59 in FIG. 57.

FIG. 60 is a section of a cell in an elastomer-filled cushioning made bythe construction shown in FIG. 56.

FIG. 61 is a schematic view, partially in section, of an apparatus whichmay be used to make a prefab, an air cell cushioning or anelastomer-filled cushioning, any of which may have embossments on oneside differing in shape from those on the other side. This uses, insequence, embossing, cross sealing and long sealing.

FIG. 62 is an elevation, in partial section, of an air cell cushioningwith one unembossed or flat side which may be made by the constructionshown in FIG. 61.

FIG. 63 is a schematic front elevation, partially in section, of analternate construction for making either an air cell cushioning or anelastomer-filled cushioning. This uses either embossing followed bysimultaneous long and cross sealing with heat or embossing followed bylong and cross sealing with adhesive.

FIG. 64 is a front elevation and FIG. 65 aplan, partially broken away,of an alternate construction using reciprocating tables to make aprefab.

FIG. 66 is a view, partially in section, taken in part along line 66-66in FIG. 65 showing details of one of the air cylinders in FIG. 65.

FIG. 67 is a plan of a portion of a prefab showing a cell constructionin which a large part of the film forming thecell walls is unaltered bythe embossing process.

FIG. 68 is an end elevation of FIG. 67.

FIG. 69 is a section on the line 69-69 of FIG. 67

FIG. 70 is a section of a cell resulting from the inflation and longsealing of the prefab, a portion of which is shown in FIGS. 67 and 68.

FIG. 71 is a plan of a portion of a prefab showing a cell constructionin which the cross sealed areas are embossed with raised areas anddepressions.

- FIG. 72 is a section on the line 72-72 of FIG. 71.

FIG. 73 is an elevation in partial section on the prefab portion shownin FIGS. 71 and 72 after it has been inflated and long sealed.

FIG. 74 is a right elevation on FIG. 73.

Referring now to the drawings, FIGS. 1 and 2 show the preferred form ofthe invention for making a prefab. A top sheet of film 10 and bottomsheet 11 enter the machine at the left. Although one sheet may bethicker or thinner than the other, they are shown as having the samethickness to simplify the drawing. The margins of sheets 10 and 11 passbetween electrical radiant heaters 12 which raise the margintemperatures close to the melting point. Each heater 12 is preferably ofthe open coil type with low mass, enabling it to come up to operatingtemperature quickly. Each sheet margin is then gripped between a sealingwheel 13 and a pressure wheel 14 which press the heated margins togetherforming margin seals shown by dotted lines 15a and 15b. Wheels 13 and 14are driven by suitable gearing (not shown) to advance the film sheets tothe right in FIG. 1.

Each sealing wheel 13 comprises a shaft 16 fixed in a metal hub 17(FIGS. 3 and 4). Metal hub 17 carries a rubber portion 18 on which isbonded a thin metal rim 19. Each pressure wheel 14 comprises a shaft 20fixed in a metal hub 21 on which is bonded a rubber working portion 22.It will be seen that this construction minimizes heat loss from themargins of the sheets as they are being sealed, gives the parts lowthermal inertia and makes it possible for them to rise quickly tooperating temperature.

Another possible construction for making margin seals is illustrated inFIGS. 5 and 6. On each side of the machine the margins of top sheet 25and bottom sheet 26 pass between sealing wheel 27 and pressure wheel 28.Above and in contact with sealing wheel 27 is a heater disc 29 having anarrow face 30. Heater disc 29 is carried on a central fiber body 31which is fixed on shaft 32. Close to the narrow face 30 is located anelectric radiant heater 33, preferably of the open coil type.

Sealing wheel 27 comprises a shaft 36 fixed in a metal body 37 which hasan annular groove 38 filled with heat insulation 39 such as fiber glass.A thin band 40 of metal that does not conduct heat well, such asNichrome, from 1 to mils thick, covers insulation 39 and is bonded tothe outer portion of the wheel body 37. Pressure wheel 28 is fixed onshaft 41 and has the same construction described for pressure wheel 14.Shafts 32, 36 and 41 are driven through suitable gearing (not shown) toadvance the film sheets and 26 to the right in FIG. 5.

In operation, the radiant heater33 raises the temperature of heater disc29. -A portion of this heat is printed or transferred by conduction toband 40, producing a narrow strip of heated metal in the center ofband40. The heat in this narrow strip is progressively transferred byconduction to sheet 25 and thence to sheet 26, thus sealing the margins.The principles are known to those skilled in the art. It will be seenthat the parts carrying heat have low mass, enabling them to rise tooperating temperature quickly.

The sheets with margins sealed by one of the methods described above nowpass into what will be termed the cross seal unit." In the preferredform of the invention shown in FIG. 1, the cross seal unit receivessheets 10 and 11 between bars 43 in an upper bar-chain assembly and bars44 in a lower bar-chain assembly. In number, bars 44 may equal or exceedbars 43. In this case, the drawings show each bar-chain assembly withthe same number of bars.

Each bar 43 and 44 is a metal tube of rectangular section. The oppositeends of each bar 43 are attached to opposite links of parallel rollerchains 45. As shown in FIG. 7, the link plate 46 of a typical chain 45is held by nut 47 on stud 48 welded to bar 43. The parallel rollerchains 45 run over fixed upper tracks 49, around sprockets 51 on shaft52, under fixed lower tracks 50 and around sprockets 53 on shaft 54.Bars 44 are similarly attached to parallel roller chains 55 running overfixed lower tracks 56, around sprockets 57 on shaft 58, over uppertracks 59 and around sprockets 61 on shaft 62. Tracks 59 may be raisedor lowered by adjusting screws (not shown).

I Therefore, those portions of roller chains 55 traveling over tracks 59may be forced upward, bringing each bar 44 into regulated pressurecontact with a mating bar 43 as the pair of bars travels to the right,carrying sheets 10 and 11 through the cross seal unit.

FIGS. 7 and 9 show how there is adhered to the upper surface 63 of eachbar 43 a sheet of glass cloth 64 on which lays any convenient number, inthis case seven being shown, of electric resistance heating ribbons 66ato 66g inclusive. FIGS. 7 and 9 show how the'ends of ribbons 66 on thenear side of the machine are supported. The ends of the ribbon pair 66aand 66b are connected by a strap 67, on each strap an ear 67a beingcrimped on a ribbon end. The ends of ribbon pairs 66c, 66d, 66s and 66fare similarly treated. A lug 68 is crimped on the end of the remainingribbon 66g. Ribbons 66 are covered with a glass cloth strip 69 of whichthe margins 69!: are folded at right angles and adhered to the sides ofbar 43. If desired, instead of glass cloth strip 69, a thin metalcovering, such as stainless steel foil coated with an electricalinsulating substance such as Tefion, may be used.

A rectangular clearance hole 43a is punched through the working surfaceof bar 43 near each end, leaving a narrow flat surface 43b to which isadhered a fiber sheet 70. To holes 70a in fiber sheet 70 are hooked theouter ends of springs 71a, 71b, 7lc and 71d. The inner ends of springs71a, 71b, and 71c are hooked into holes 67b in straps 67. The inner endof spring 71d-is hooked into lug 68. Also secured in lug 68 is one endof a jumper 72 the other end being soldered to contact plate 73 bondedto fiber sheet 70. The above-described construction is duplicated on thefar side so that springs 71 on each end of bar 43 maintain continuoustension in ribbons 66, holding them firmly in place despite theirexpansion and contraction due to heating and cooling.

As shown in FIG. 10, each bar 44 in the lower bar-chain assembly has aflat working surface to which is adhered a rubber sheet 74 covered byglass cloth strip 75 of which the margins 75a are folded at right anglesand adhered to the sides 'of bar 44. Located on each side of the machinenear the beginning of the lower horizontal path of contact plates 73 arestationary brushes 76 in the form of leaf springs, one of these beingshown in FIG. 1. The free end 76a of each brush 76 is positioned to wipeover.contact plates 73 in the manner shown in FIG. 11. As shown in FIG.1, a fiber wheel 77 with lobes 77a is driven from sprocket shaft 62through a suitable mechanical connection indicated by dashed line 78. Inthe path of lobes 77a a contact spring 79 is located so that, as eachlobe 77a passes, it forces contact spring 79 into electrical contactingrelationship with spring 81. FIG. 12 shows how the above parts andribbons 66 of a typical bar 43 are connected. A source of electricity 82is provided to energize the ribbons 66.

To better describe the operation of the machine, the term cross sealpath will be used for the path traveled by a bar 43 as it mates with abar 44 to grip and carry the film sheets through the machine, and theterm cross seal time for the time the mating bars take to travel thispath. As each bar 43 starts on the cross seal path, its associatedcontact plates 73 begin to slide over brushes 76. At this point lobe 77aforces contact spring 79 against contact spring 81, closing theelectrical circuit and starting an impulse of current flowing throughribbons 66. This impulse continues to flow during the early part of thecross seal time as contact plates 73 slide over brushes 76. Beforecontact plates 73 and brushes 76 separate, lobe 77a leaves contactspring 79, springs 79 and 81 separate, ending the impulse of current. 1

The heat generated in ribbons 66 forms between sheets 10 and 11 undereach ribbon 66 a cross seal 83 which cools during the balance of thecross seal time, this process being known as impulse sealing. FIG. 13shows that, as a result of cross sealing, the sheets now embody crosschannels 84. Each cross seal 83 meets margin seal 15b on the far side ofthe sheets but ends a short distance away from margin seal 15a on thenear side. This leaves a longitudinal access channel 85 communicatingwith all the cross channels 84.

The film sheets leaving the cross seal unit retain some heat which islargely removed by a blast of air from supply ducts 86 shown in FIG. 1.Part of the heat generated in ribbons 66 is conducted to bars 43 and 44,raising their temperature and thus limiting their capacity to cool thefilm sheets. Therefore, on the near side of the machine near the returnpath of bars 43, there is located a supply duct 87 through which coldair is blown into the bars. The cold air flows through the bars and intoreceiving duct 88 from which it returns to a cold air supply system (notshown). A similar arrangement removes heat from bars 44, the cold airsupply duct 89 being shown in FIG. 1. The air ducts are shown inelementary form to simplify the drawings. In practice, they may be largeenough to cool all the bars in the upper and lower bar-chain assembliesin their return paths. The cross seal unit described is designed to sealfilms up to about 10 mils thick or a total thickness of 20 mils. Theequipment may be adapted to seal thicker films by using heating ribbonsin bars 44 also, giving them the same construction as bars 43. In thisway more heat can be delivered to the areas to be sealed.

A first alternate construction for making cross seals is illustrated inFIGS. 14 and 15. Top sheet 90 and bottom sheet 91, joined by marginseals 92a and 92b, pass in turn around pressure roll 93, drum 94 andstripping roll 95, the rolls and drum being driven in synchronism bysuitable gearing (not shown).

The surface of pressure roll 93 is covered with a rubber layer 93a. Drum94 is a hollow metal cylinder sealed at each end to a flange 96. Eachflange 96 is carried on a shaft 97 having a hold 98 leading to theinterior of drum 94.

Looking at FIGS. 16 and 17, it will be seen that a sheet of glass cloth99 is adhered to drum 94, the glass cloth 99 supporting electric heatingribbons 100 laying parallel to the drum axis. Ribbons 100 are covered bya sheet of glass cloth 101 or thin metal sheet as previously describedfor bar 43.

Flange 96 carries a fiber ring 102 holding copper contact segments 103.Attached to each segment 103 by screws 104 is a leaf spring 106 to theouter end of which a bent lug 107 is secured by bolt 108. Each lug 107is crimped on the end of a ribbon 100. This construction is duplicatedon the far side of the drum, thus placing each ribbon 100 in tensionbetween two leaf springs 106. A stationary contact brush 109 is locatednear each end of drum 94 so that it bears on segments 103. A source ofelectricity is connected to brushes 109, one brush 109 being shown inFIG. 14.

Surrounding the major portion of the outer surface of drum 94 traversedby sheets 90 and 91 is a metal sheet 110 carrying side walls 111, eachat right angles to the axis of drum 94, and end walls 112. These sheetmetal parts in conjunction with the outer surface of the drum 94 form anair chamber 113 supported by means not shown and supplied with air underpressure through pipe 114.

In operation, asa ribbon 100 passes through the pressure zone betweenpressure roll 93 and drum 94, the associated segments 103 wipe overbrushes 109. This sends an impulse of current through the ribbon 100 andforms a cross seal 115 between sheets 90 and 91.'Each cross seal 115cools as it travels the rest ofthe way around the drum. Drum 94 may becooled by pumping fluid through hollow shaft 97.

The air under pressure in chamber 113 forms a blanket that holds sheets90 and 91 in contact with each other and with drum 94 during the timethe cross seals are cooling. Air entering chamber 113 also escapes underside walls 111 and end walls 112, helping to cool the cross seals 115.Air chamber 113 may not be required for sealing relatively thick films.Other means may be used to hold the films in contact during the coolingtime if desired. For example, a belt as wide as the film sheets may bearranged to partially encircle the outside of the drum, the belt beingarranged to travel in a closed path and kept in tension so as to exertpressure on the film sheets.

A second alternate construction for making cross seals is shown in FIG.18. Top sheet 120 and bottom sheet 121 pass around pressure roll 122,drum 123 and stripping roll 124. Rolls 122 and 124 are of metal coveredrespectively with rubber layers 122a and 124a. Drum 123 is carried onflanges 125 and is fluid cooled through pipes, not shown. As shown inFIG. 19, drum 123 has adhered to its outer-surface a glass cloth 126supporting a sheet metal covering 127 of low conductivity metal, such asNichrome, from one to mils thick. A hollow metal heater roll 128,carried on hubs 129, supports lengthwise bars 130 which are pressedagainst sheet metal covering 127 as roll 128 rotates. Roll 128 is drivenso that the peripheral speed of bars 130 is the same as that of sheetmetal covering127.

In operation, heater roll 128 may be heated by circulated hot oil or byan inserted electric resistance heater (not shown). The bars 130 printor transfer transverse lines of 1 heat to the sheet metal covering 127.This heat is stored, then transferred by conduction to sheets 120 and121, forming cross seals in a manner known in the art. If desired,margin seals may be made in the same operation. This may be done asoutlined in FIGS. 20 and 21 by attaching a disc 132, preferably ofbrass, to each hub 129 by bolts 133. Disc 132 is also shown as anoptional element in dashed lines in FIG. 19. If desired, an air chamberor partial circumferential belt may be added to the construction to holdthe film sheets in contact with each other and with the drum 123, asdescribed in connection with FIG. 14.

After being cross sealed by one of the methods described above, thesheets pass into what will be termed the embossing unit, now to bedescribed. In the preferred form of the invention shown in FIGS. 1 and2, sheets 10 and 11 leave bars 43 and 44 and pass between radiantheaters 141 which raise their overall temperature to the vicinity of thesoftening point. The sheets then pass between and are embossed by maleroll 142 and female roll 143. Male roll 142 comprises flanges 144carried on shaft 145. Flanges 144 support cylinder 146, the surface ofwhich is coated with a rubber layer 147, shown in FIGS. 22 and 23. Onrubber layer 147 is bonded a sheet ofthin metal 148, such as copper,formed into a pattern of bosses I49, leaving spaces between the bossesand rubber layer 147.

If desired, these spaces may be filled with rubber. Female roll 143,comprises flanges 151 carried on shaft 152. FIGS. 23 and 24 show how theflanges 151 support lengthwise bars 153 and annular bars 154, forming agrid with rectangular openings that receive bosses 149. The embossingroll 142 may be heated, if desired, by radiant heater 157.

Sheets 10 and 11 are presented to the embossing rolls so that crossseals 83 fall on bars 153. Sheets 10 and 11 are embossed at the sametime forming, between adjacent cross seals 83, a row of embossments 158ain sheet 10 and 158); in sheet 11. FIGS. 25 and 26 show how theembossments are separated by unembossed discontinuous strips 159 runninglengthwise of the sheets, and by seals 83 running cross wise of thesheets, which now form a prefab. If the temperature of the film sheetsis properly controlled, they do not adhere to each other afterembossing. However, if desired, a release agent may be applied to thecontacting sides of sheets 10 and 11 before film fabrication begins. I

An alternate embossing method using a vacuum is shown in FIGS. 27 and28. Top sheet and bottom sheet 171 pass between and are softened byradiant heaters l72,'then pass around feed roll 173, embossing roll 174and stripping roll 175. Embossing roll 174 comprises two flanges 176turning on a stationary hollow shaft 177. Flanges 176 support a metalcylinder 178 shown in FIG. 30. As shown in FIGS. 29 and 30, cylinder 178is covered with an insulating rubber layer 179 having depressions 180formed therein. From each depression 180 a port 181 leads through therubber layer 179 and cylinder 178. In the interior of the cylinder, asshown in FIG. 30, stationary hollow shaft 177 has a port 182 connectedto a manifold 183 in a stationary shoe 184 supported by shaft 177. Theinterior surface of cylinder 178 slides over shoe 184. Thus, vacuum maybe applied to sheets 170 and 171 forming, as shown in FIG. 29,embossments 185a in sheet 170 and 1851; in sheet 171. The rubber layer179 prevents undue loss of heat from the film sheets and helps giveshort start-up time.

The configuration of embossments produced by either method describedabove and shown, for example, in FIGS 25 and 26, is only suggestive.They may be made in any convenient size and shape desired and arrangedin any convenient number per square foot of film structure as long asthey are aligned in longitudinal rows and in transverse rows between thecross seals. Embossments, for example, in the form of truncated pyramidswith either a square or oblong base may be more useful than those shown,especially where heavy objects are to be cushioned. Also, cushioningwith such embossments offers more contact area where it is desired toadhere the cushioning to corrugated board or paper. After embossing, thefilm structure constitutes a prefab which may be wound into a roll (notshown) for shipment to the user who can then convert it into finishedcushioning. During the winding process the embossments are crushed andcompacted, giving the roll high density.

The conversion equipment for making air cell cushioning from the prefabis shown for the preferred form of the invention in FIGS. 31 and 32.Sheets 10 and 11 are inflated through access channel 85, pass aroundwheels 187 on shaft 188, travel around cylinder 189 on rings 190, duringwhich travel they are long sealed by tape strands 191 and finally passunder discs 192 on shaft 193. FIG. 33 shows how access channel 85 isformed into the semblance of a tube which is slipped over pipe 186. Asshown in FIG. 34, pipe 186 has a lengthwise row of slots 194 facing thecenter of the prefab. Air under pressure is forced through the pipe 186,out slots 194, through access channel 85 and cross channels 84. The airliftseach embossment 158a in sheet 10, reversing its configuration fromconcave to convex, thus giving, with its mating embossment 158b, aninflated air cell, shown in FIG. 35. In FIG. 31 the embossment 158a isshown partly lifted as it is being inflated. By alter- A knife 195,shown in FIG. 34, on the side of pipe 186 cuts sheets and 11 apart attheir near side margin so that the sheets may pass over the pipe. Sheets10 and 11 with cells 158 inflated now pass around wheels 187, thediscontinuous strips 159 riding on the rims of the wheels. The pressurebetween strips 159 and wheels 187 seals off cells 158, retaining air inthe cells during the passage of the sheets around the wheels. The rings190 on which sheets 10 and 11 travel around cylinder 189 are illustratedas being made of rubber, but may be made of metal if desired. The ringsare suitably spaced along the cylinder axis and bonded to its surface asshown in FIG. 35. Each end of cylinder 189 is carried on a flange 196fixed on a shaft 197.

As the sheets travel around the cylinder on rings 190 they pass undertensioned parallel tape strands 191. Tape strands 191 ride on thesheets, pressing them against rings 190 through any convenient arc oftravel, in this case about 30, then leave the sheets and travel arounddiscs 192 on shaft 193, heater roll 200 on hollow shaft 201, aroundfiber discs 198 on shaft 199, then back to the film sheets. The tapeforming strands 191 is endless and is wound around the assembly of discs198, discs 192 and heater roll 200 in helical fashion. From the portion191b at the end of its helical path on the near side of the machine, thetape is returned, as shown at 191a, to the beginning of its path andkept in tension by a suitable arrangement of pulleys (not shown).

The tape is preferably stainless steel, about ,4. inch wide and from oneto 10 mils thick. Its section may be rectangular but is preferablytrapezoidal, as shown in FIG. 36, with the widest side 191a contactingthe film sheets. Such tape is a standard production item and readilyavailable.

Shafts 193, 199 and 201 are journalled at each end in a plate 202 andturned by means not shown to drive tape strands 191 at the surface speedof rings 190. Tape strands 191 are kept in their paths by tracking pins203 held in bars 204 sup ported by plates 202. If desired, plates 202with the whole tape transport mechanism may be arranged to liftvertically to facilitate servicing. The unit stress in the tape beingwell within the elastic limit, the predictable life of the tape isindefinitely long, of the order of decades.

Heater roll 200 is maintained at a temperature near the softening pointof the film by inserted electric heaters (not shown) or by circulatedhot oil. The hot tape strands 191 leaving the heater roll 200 retainheat as they pass around fiber 7 discs 198. Then, as they begin their.ride on top sheet 10, most of the heat stored in the tape strands istransferred to strips 159, forming long seals 159a. Because of thetrapezoidal section, more heat is stored near the center of the tapeand, therefore, more heat is transferred to thecenter of each strip 159.This gives a-desirable heat distribution across the cross seal sectionand helps maintain the strength of the film at the edge of the seal.Thus, this construction makes available a novel and efficient method oflongitudinal impulse sealing.

To prove the effectiveness of this sealing method, apparatus of thistype was constructed to make the long seals. The apparatus was comprisedof a drum 14.5 inches in diameter and 3 inches wide made from 18 gaugesheet steel and the 3 inch periphery covered with cotton cloth. The drumwas mounted for free rotation on a horizontal shaft.

A tape 5/32 inch wide and 9 feet long was cut from a coil of Grade Aspring temper phosphor bronze sheet 2 mils thick as manufactured by TheT. E. Conklin Brass & Copper Co., Inc. This tape was formed into a loopby soldering the ends together. A system of four wheels was used tocarry approximately half the tape in a 180 wrap around the cloth-coveredsurface of the drum, one of the wheels being driven by a motor. Theother half of the tape loop was carried over an adjustably mounted wheelused to regulate the tension in the tape, the tension being read by aspring balance. No release agent was used on the tape or on the clothcovering the drum.

Between the wheel feeding the tape to the drum and the point of contactof the tape with the drum, a length of 6 inches of tape was heated bytwo parallelcoils of Nichrome wire l0 mils in diameter, the coils beingspaced about inch from the long, and carried 24 turns per inch. Thecoils were connected in series to a l20 volt supply and placed within asemicylindrical polished sheet metal reflector.

This apparatus made perfect long seals between two sheets of 1 mil thickpolyethylene sheet when operated at a rate of 27 feet per minute. Thetape tension did not seem to be critical and could be varied from 0.8pound to 2 pounds without any apparent effect upon the quality of thelong seal.

As the film sheets leave rings 190, each air cell 158 is now sealed onall sides. The pressure and temperature of the air forced through pipe186 will affect the firmness of the cells. The colder the air, the moreit will expand as it subsequently rises to room temperature and thefirmer will be the cells. Thus, the equipment can operate at atmosphericpressure and make cushioning having internal air pressures in the cellsabove atmospheric pressure, producing tension in the cell walls, andgiving maximum cell volume. For a given cell configuration, therefore,this process can produce, at atmospheric pressure, the maximumcushioning volume per pound of film used.

The air cell cushioning is now complete as made by the preferred fonn ofthe invention operating on two sheets of film-If desired, theprefab-making equipment shown in FIG. 1 may be combined with theconversion equipment shown in FIG. 31 giving one integrated machine fordirect production of finished cushioning. Automatic lengthwise-slittingand cutting-to-length devices may be added to the machine if desired.

Another way to use the invention is to supply the prefabmaking equipmentshown in FIG. 1 with a flattened film tube from a supply roll ordirectly from an extruder, thus producing a prefab with margins alreadyjoined. In this case, the margin. sealing equipment shown in FIG. 1 neednot be used.

Still another way to use the invention is to omit the margin sealingdevices shown in FIG. 1 and supply the equipment with two sheets offilm, thus producing a prefab with margins unsealed. The equipment forconverting such a prefab into cushioning differs from that shown in FIG.31 only in that portion used for inflating the cells. Therefore, onlythis portion of the equipment will be described and is shown in FIGS.37, 38

and 39, associated with certain other parts shown in FIG. 31, thereforegiven the same designations. These parts are the pipe 186, the wheel187, and the shaft 188.

On each side of the machine a pulley 206 on the near side end of drivenshaft 188 drives upper belt 207 which passes over idler pulley 208.Below shaft 188 a pulley 209 on driven shaft 211 carries lower belt 212which passes over idler pulley 213. The margins of sheets 214 and 216are pressed together and carried forward by belts 207 and 212. As shownin FIGS. 38 and 39, on the near side of the machine the sheets arespread apart between their margins and the ends of the cross seals 217to accomodate air delivery pipe 186. FIG. 37 shows how embossments 2180in sheet 214 and 21812 in sheet 216 are separated by air pressure toform cells 218.

Although the heater roll 200 shown in FIG. 31 heats the tape strands byconduction, other heating methods may be used if desired. For example,as a first optional method, roll 200 may be unheated and a radiantheater (not shown) located near the tape strands as they pass from roll200 to discs 198. Or, as a second optional method, the tape strands maybe passed through a horizontal air duct mounted across the machine, hotair being forced through the duct to heat the tape strands.

A third optional construction for heating the tape strands is shown inFIG. 40. This is designed for tape of rectangular section, the verticalstrands being shown at 250. The strands are heated by roll 251 on hollowshaft 252 in which an electric heater (not shown) may be inserted orthrough which hot oil may be pumped. As shown in FIG. 41, there areformed on the surface of roll 251 parallel circumferential ridges 253adapted to heat only the central part of tape strands 250. Thus, moreheat may be stored in the center of the tape strands giving a long sealof desirable characteristics.

An alternate construction for making long seals is shown in FIG. 42 withauxiliary devices omitted. This uses tape strands above and below thefilm sheets as the sheets travel over a cylinder. The construction isthe same as that shown in FIG. 31 with the addition of tape strandsbelow the film sheets. Therefore, the principal parts shown in FIG. 31,except the film sheets designated in that drawing, are reproduced inFIG. 42 and require no further description.

In FIG. 42, top sheet 259 and bottom sheet 260 with cells 261 inflatedpass under wheels 187. After leaving wheels 187 the sheets pass betweenhot upper tape strands 191 and hot lower tape strands 262 which travelaround cylinder 189 on the rubber rings 190. As lower tape strands 262leave rings 190 they pass in helical fashion around solid roll 263,heater roll 264 and back to rings 190 in a manner similar to thatdescribed for tape strands 191 in FIG. 31. FIG. 43 shows the relation ofthe parts while long seals are being made. This method is well adaptedto long sealing relatively thick films because heat is applied to bothfilms where they are to be heat sealed.

A second alternate construction for making long seals is shown in FIG.44. This uses tape strands above and below film sheets traveling in astraight line. Top sheet 300 and bottom sheet 30] pass between and arecarried to the right by upper tape strands 302 and lower tape strands303. The endless tape forming upper strands 302 passes in helicalfashion around fiber discs 304, discs 306, solid roll 307, heater roll309, then returns to discs 304 in the general manner described for tapestrands 191 in FIG. 31.

Lower tape strands 303 are similarly associated with fiber discs 311,discs 312, roll 313 and heater roll 314. Stationary shoes 316 supportedby transverse bar 317 and stationary shoes 318 supported by bar 319press tape strands 302 and 303 respectively against film sheets 300 and301, sealing off the air cells 320. The relative position of the partsduring the sealing process is shown in FIG. 45. This method is alsoadapted to scaling relatively thick films.

A third alternate construction for making long seals uses the mechanismshown in FIG. 46. This uses wheels, each one similar to wheel 13 in FIG.3, with heated rims that apply heat to the strip areas to be longsealed. Top sheet 350 and bottom sheet 351 pass under discs 352 on shaft353, over rubber rings 354 on cylinder 356 and under discs 357 on shaft358. The thin metal rims 359 on fiber or rubber wheels 361 pass throughslots (not shown) in metal reflector 362 so that rims 359 receiveradiation from heater 363. Heat stored in rims 359 is transferred tofilm sheet 350, thence to sheet 351, forming long seals separated by aircells 364.

Other methods may be used to heat the wheel rims 359. They may bearranged to pass through slots in a horizontal air duct crosswise of themachine (not shown) and heated by hot air forced through the duct. Thewheel rims may be arranged to run against a heated roll, picking up heatby conduction, or they may be heated by a high frequency device.

Long seals may also be made by other methods than those described. Jetsof hot air may be directed against the strip areas to be heat sealedfollowed by pressure rolls to squeeze the hot film together, orultrasonic energy may be applied to the strip areas to be heat sealed.These methods are known in the art.

An alternate construction for making a prefab is shown in FIGS. 47 and48. This uses, in sequence, embossing and cross sealing. Top sheet 400and bottom sheet 401 are embossed by equipment such as is shown in FIG.1, this being indicated by block symbol 402. The embossments producedare designated 400a and 401a. The embossed sheets pass into the crossseal unit comprising upper bar-ehain assembly 403 and lower barchainassembly 404. The bars in the upper bar-chain assembly 403 are built thesame as the corresponding bars in FIG. 1 and are given the samedesignation 43. In FIG. 48 are detailed a portion of a bar 43, theassociated glass cloth 64, heating ribbons 66 and glass cloth 69.

Each bar 406 in the lower bar-chain assembly 404 carrieslengthwiserubber ridges 407 which pass between embossments 401a andpress the transverse unembossed portions of the film sheets against theglass-cloth-covered heating ribbons 66 while the cross seals are beingmade. This equipment may be used as described or suitably modified asoutlined before to produce prefabs from either sheet or tube stock. Anyprefab thus made may'be converted into air cell cushioning using asuitable method previously described.

An alternate construction for making air cell cushioning is shown inFIG. 49. This uses, in sequence, embossing, long sealing and crosssealing. To simplify the description it will be assumed that theequipment is supplied with a flattened film tube 500 pictured as topportion 501 laying on bottom portion 502. The tube 500 first passesthrough embossing unit 503, then through inflation and long sealingequipment shown by symbol 504, this being one of the types describedbefore, such as that shown in FIG. 31. Tube 500 now passes through across seal unit shown by symbol 507 comprising upper and lower bar-chainassemblies having the general construction shown in FIG. 1 except that,as shown in FIG. 50, each bar 508 in the lower bar-chain assembly haslengthwise rubber ridges 509 and each bar 511 in the upper bar-chainassembly has attached sheet metal portions 512. A section on eachportion 512 is in the form of a triangle having sides 512a. Theflattened apex of portion 512 is covered with a glass cloth strip 516against which heating ribbon 517 is held by glass cloth strip 518.

This construction thus maintains heating ribbons517in a plane parallelto and spaced from bar 511. A suitable similar construction (not shown)holds tension springs and contact plates associated with heating ribbons517 in the same plane as ribbons 517, these parts functioning in themanner described for FIG. 9. The completed cushioning, with cells 528completely sealed, is shown leaving the cross seal unit 507. It waspreviously noted that a flattened film tube was fed to this equipment,but separate sheets may be used, if desired. If so, the margins may besealed prior to embossing or the margins may be left unsealed andsuitable equipment such as that shown in FIGS. 37 and 44 used forinflation and long sealing.

An alternate construction for making a prefab using only cross sealingis shown in FIG. 51, and a method using bunch folds" for converting thisprefab into air cell cushioning is shown in FIG. 52. Again, to simplifythe description, it will be assumed that a flattened film tube 600,pictured as two sheets, is supplied the equipment. The tube 600 passesthrough a cross seal unit such as that shown in FIG. 1, this being shownby symbol 601. As detailed in FIG. 53, this makes a prefab 602 withcross seals 603 and cross channels 604 starting at the far edge 605 ofthe tube. Cross seals 603 end a short distance away from the near edge606. FIG. 51 shows the prefab 602 wound into a roll 607 for conveniencein shipment.

In FIG. 52, prefab 602 unwinds from roll 607 and passes through longseal equipment such as that shown in FIG. 31, this being pictured bysymbol 608. As cross channels 604 are inflated, they are converted intofilm tubes (not shown) extending across the film structure. Theequipment 608 presses the walls of the film tubes together on the longseal lines forming finished cushioning 609 with sealed cells 610 by amethod known in the trade as"bunch folding. A typical cell 610 thusformed is detailed in elevation in FIG. 54 and in plan in FIG. 55, thewrinkles or bunch folds being indicated at 611.

The formation of the transverse film tubes during the inflation processcauses the film tube to shrink along its length. Thus, for each tenlinear feet of finished cushioning 609 leaving the equipment 608, from12 to l5 feet of prefab 602 may be drawn from supply roll 607, dependingon the degree of inflation of the cells. If desired, the equipment shownin FIGS. 51 and 52 may be combined to form one machine for making aircell cushioning.

A construction that can make an air cell cushioning or anelastomer-filled cushioning is shown in FIGS. 56 and 57. It employs along seal mechanism similar to that shown in FIG. 44. Top sheet 700enters the equipment around roll 701 and bottom sheet 702 enters aroundroll 703. Upper tape strands 704 pass around and receive heat fromheater roll 705, then pass around and are pressed by fiber discs 706against sheet 700, pass around discs 707 and roll 708, then return toheater roll 705. Lower tape strands 709 are similarly associated withheater roll 710, fiber discs 711, discs 712 and roll 713. Necessaryauxiliary devices, previously described, are omitted. Discs 706 arecarried on shaft 714. Discs 707, 711 and 712 are similarly supported,but their associated shafts are not designated.

Connected to header 715 are pipes 716 located between film sheets 700and 702 in the horizontal plane of and between the sealing portions ofthe upper and lower tape strands-Pipes 716 extend through the mechanism,their ends being shown at 7160. As shown in FIGS. 57 and 58, the tapestrands make long seals 717 on each side of each pipe 716, forming longchannels, not designated, between long seals 717. The tape strands alsomake margin seals 718.

As the film sheets travel past pipe ends 716a, air forced through thepipes inflates the long channels into film tubes 719, each having asection as shown in FIG. 59. The formation of film tubes 719 causes thefilm structure to shrink in width as shown in the plan view, FIG. 57.The film structure nowpasses through a cross seal unit similar to thatshown in FIG. 1, but having bars-modified as shown in FIG. 50, this unitbeing shown by symbol 721. This cross seals and bunch folds the filmtubes 719, giving finished air cell cushioning shown at 722. The pipes716 may be used to force a paste or foam elastomer 723 into the tubes719 instead of air, giving a section through a cell of the finishedproduct the appearance of FIG. 60.

A construction that can make a prefab, an air cell cushioning or anelastomer-filled cushioning is shown in FIG. 61. This comprises asequence of embossing, cross sealing and long sealing units. It includesembossing units 800 and 801 which may be similar to that shown inFIG. 1. If desired, the embossments made by unit 800 may differ in shapefrom those made by unit 801. The construction also includes twoparallel, adjustably-spaced driven shafts 802 and 803 carrying,respectively, disc assemblies 804 and 806. It includes two reservoirs807 and 808 and a third driven shaft 809 carrying discs 811. It includesa cross seal unit 812 which may be similar to that shown in FIG. 1 butwith the bar constructions illustrated in FIG. 50 and a long seal unit813 such as that shown in FIG. 31 modified by adding the inflationmechanism of FIG. 37.

To make the prefab, reservoirs 807 and 808 need not be used and areempty. A first sheet of film 816 is fed through embossing unit 800,receiving embossments 816a in a form selected for illustration as atruncated pyramid with square base, under reservoir 807 and over discs804. A second sheet 817 is fed through embossing unit 801, receivingembossments 817a having the same base configuration as embossments 816abut with a rounded outer profile, under reservoir 808 and over discs806.

Sheets 816 and 817 are pressed together as they pass between discs 804and 806, the embossing units being synchronized so that each embossment816a in sheet 816 mates with and totally communicates with an embossment817a in sheet 817. The two sheets now travel together around discs 81]and through cross seal unit 812 forming a prefab indicated at 819 whichmay be wound into a roll (not shown) for shipment. As the margins arenot sealed, the air in the mating embossments will be expelled throughthe spaces between the cross seals and the embossments will becollapsed, giving a roll of high density.

For direct production of air cell cushioning, the prefab, indicated at819a, continues its travel, going through long seal unit 813, emergingas finished cushioning 821 with individually sealed cells 822. Inflationduring long sealingis not necessary, but is desirable to assure firmcells. If desired, air may be blown through the pipe 823 to helpmaintain the shape of the embossments prior to the sealing operation.

This equipment can also make air cell cushioning with one unembossed orflat side by making one embossing unit, such as 800, inoperative. FIG.62 shows such a product asa first sheet 826 paired with a second sheet827, the latter having embossments 827a. This is useful in makingpackages or containers because the flat side may be more readily adheredto a sheet of paper, cardboard or corrugated board. If desired, sheet826 may be made thicker and of more rigid material than sheet 827 andthe resultant product made directly into containers.

To make an elastomer-filled cushioning, the reserviors 807 and 808 arefilled with a paste or foam elastomer 824. As the sheets travel beneaththe reservoirs, the embossments in each sheet are filled with elastomer824. The structure then passes through the crossseal unit 812 and longseal unit 813, completing its fabrication. An elastomer-filledcushioning with one flat side may also be made, if desired, as explainedin connection with FIG. 62.

Optionally, the elements of the construction shown in FIG. 61 may berearranged to make cushioning with the cells filled with air orelastomer. This may be done by reversing the positions of cross sealunit 812 and long seal unit 813 and needs no illustration.

Another alternate construction for making air cell cushioning orelastomer-filled cushioning is shown in FIG. 63. This uses embossingfollowed by simultaneous long and cross sealing or by adhesiveapplication. Certain parts already described in detail have been giventhe same designations previously used. Both roll 143 and 143a in FIG. 63have the same construction as female roll 143 shown in FIG. 1 and indetail in FIG. 24 with lengthwise bars 153 and annular bars 154 forminga grid with rectangular openings in the outer portion of the roll. Aheater roll 850 is located so as to roll against the bars forming thesurface of roll 143 in FIG. 63. Rolls 143 and 143a are driven bysuitable gearing (not shown) so that each bar 153 in roll 143 contactsits counterpart in roll 143a. A row of discs 851 on shaft 852 is locatedadjacent to roll 143a.

Adhesive coating equipment is provided including reservoir 853, diprolls 854 and coating discs 856. A first sheet 857 is passed throughembossing unit 858, this unit being of the type shown in FIG. 1,producing embossments 857a. A second sheet 859 is similar processed,producing embossments 859a. The embossing units are synchronized so thateach embossment 857a is brought into mating and totally communicatingrelationship with an embossment 859a as the sheets pass between rolls143 and 143a.

To make heat sealed cushioning, the adhesive coating equipment is madeinoperative and the heater roll 850 brought up to operating temperature.Sheets 857 and 859 are presented and passed through rolls 143 and 143aso that the bars 153 and 154 are aligned with the unembossed areas ofthe sheets, thus making both long and cross seals at the same time, theopenings between the bars allowing passage of the embossmerits in thesheets. The seals thus formed cool as they travel around the surface ofroll 143a and around discs 851. If

desired, the working surfaces of the bars in roll 143a may be coveredwith a layer of rubber to better distribute the sealing pressure. If thesheets being processed are relatively thin, that is, of the order of 1mil thick, the embossments 857a and 859a may not retain their shape wellenough to give cells of the desired firmness. In this case, air may beblown into the cmbossments through nozzle 861 as they enter rolls 143and 143a, assuring firm cells.

To make cushioning using adhesive, heater roll 850 is made inoperativeand adhesive 861 placed in reservoir 853. As sheets 857 and 859 passthrough the equipment, they are coated with adhesive by coating discs856, then are pressed together by rolls 143 and 143a. Cushioning withone flat side may be made as explained in connection with FIG. 61. Tomake cushioning with an elastomer filling, a paste or foam elastomer maybe supplied through nonle 861. Either heat sealing or adhesiveapplication may be used to seal off the cells.

Another alternate construction for making a prefab is shown in FIGS. 64and 65. This uses reciprocating tables with an operating sequence ofcross sealing, then embossing. A film tube 900, pictured as two sheets,is drawn at constant speed through reciprocating tables adapted to crossseal and emboss the tube. In FIG. 64, piston rods 901 are fixed to lowertable 902 which is carried on shoes 903 that slide on stationary ways904. As detailed in FIG. 66, attached to each piston rod 901 is a piston906 sliding in cylinder 907 which is attached to the upper table 908.Lower table 902 is covered with a rubber pad 909. The tables 902 and 908may slide to the left, the respective alternate positions beingdesignated 910 and 911. The lower surface of table 908 is divided alongits length into four working sections 908a, 908b, 908c and 908d, ofequal length. Sections 908a, 908c and 908d may be heated to controlledtemperatures by devices not shown while section 908b is not heated ormay be cooled by circulated fluid.

Section 908a carries any convenient number, in this case four beingshown, of cross seal bars 912a adapted to make part of each of fourcross seals 913, starting at margin 900a on the far side of the filmtube and extending toward its center a distance equalto one third of itswidth. Section 908a also carries four cross seal bars 9l2b transverselyaligned with bars 912a and adapted to make another part of each of thefour cross seals 913, starting a short distance from the near margin 90%and extending toward the center of the film tube a distance equal toabout one-third its width. Section 9080 carries cross seal bars 914located in spaced relationship to bars 912a and 912b. Section 908dcarries bosses 915 arranged in lengthwise and transverse rows, thetransverse rows of bosses being located in spaced relationship withcross seal bars 912a, 912b and 914.

In operation, film tube 900 is drawn to the right at constant speed bydevices not shown. Air is forced into the space below and exhausted fromthe space above pistons 906 when the tables are in positions 910 and911. The tables close and move to the right with the film tube at thesame speed as the tube for a distance equal to about two-thirds thelength of one section such as 908a. The tables then open and return tostarting position with a quick-return motion at about twice the speedthey moved to the right, thus enabling the table sections to operationcontinuously on the film tube. Thus, portions of the film tube 900 areprogressively cross sealed with the pattern shown in FIG. 53, thenembossed so that the embossments lie between the cross seals and have across section of the general form shown in FIG. 26. The prefab thus mademay be wound into rolls for later conversion into air cell cushioning byany suitable method previously described.

In a freshly formed cross seal, the film substance at the seal lineishot and soft, lowering the tensile strength of the film tube. Crosssealing only part of the film tube at one time enables the tensionestablished in the film tube to be transmitted always by one relativelycool section.

An operation sequence of embossing followed by cross sealing may beobtained, if desired, by locating bosses 915 in section 908a, bars 912ain section 908b, and bars 914 in section 908d. With this equipment aprefab may be made from separate film sheets, if desired, then convertedinto cushioning by suitable methods previously described.

The previous description covers some of the more useful types of cellconstruction. However, the versatility of the heat sealing methods allowmany other useful types of cell construction to be made. These will nowbe outlined.

In the embossing methods described, the film in each cell wall wasaltered and made thinner than it was originally. The

product of these methods will be called the embossed cell construction.In contrast, in the cell construction shown in FIGS. 67, 68, 69 and 70,the film in each cell wall is largely unaltered by the embossing action.Top sheet 920 and bottom sheet 921 are first processed by suitabledevices to make margin seal 922 and cross seals 923. The sheets are nowembossed simultaneously with a grid pattern of troughs or valleys 924.Thus, the rectangular film area 926 in sheet 920 and area 927 in sheet921 are not embossed. The sheets now form a prefab which may beconverted into cushioning by the device of FIG. 31. This inflates thecells and makes long seals 928. Film areas 926 and 927 thus become theupper and lower cell walls. This will be called the embossed troughconstruction.

Another useful cell construction is illustrated in FIGS. 71 and 72showing the prefab and FIGS 73 and 74 showing a portion of the completedcushioning. Top sheet 930 on bottom sheet 931 are first processed toproduce cross seals 932. The sheets then enter an embossing mechanism ofa type described before. This forms the cell wall embossments 933 insheet 930 and 934 in sheet 931. At the same time, the film in and nearthe cross seals 932 is also embossed with small raised areas 936 anddepressions 937, all having the same general shape resembling a smallcircular mound. The parallel discontinuous strip area 938 in sheet 930and area 939 in sheet 931 are provided for subsequent long sealing.

In the completed cushioning shown in FIGS. 73 and 74, the effect of theraised areas 936 and depressions 937 is to partially fill the spacesbetween the cells. This gives a more rigid type of cushioning suitablefor many applications.

The cross sealing and long sealing methods described are especially welladapted to the sealing of composite or laminated films. An especiallyuseful composite film, as explained in more detail before, comprises arelatively thick layer of polyethylene and thin layer of vinylidenechloride. The latter will be called by its trade name, Saran.

A first method of making cushioning from such a composite film is toprocess two superimposed film sheets so that the polyethylene sides arein contact at the areas to be heat sealed. During heat sealing-the heatmust pass through the Saran to seal the polyethylene. Saran has a highermelting point than polyethylene so the heat does not alter it and itsintegrity is maintained.

A second method is to superimpose two sheets so that the Saran sides arein contact. The cross sealing and long sealing equipment described willeffectively seal the Saran sides together in spite of the fact that theheat must pass through the polyethylene which has a lower melting pointthan Saran.

In the above description of the cellular cushioning material of thisinvention, the cells are described as being filled with a resilient,compressible gas such as air or a compressible solid substance such as afoamed elastomer. It should be noted, however, that incompressible,deformable materials such as solid elastomers or liquids can be used toadvantage for some purposes. In this instance, the resiliency of thepackaging material will result from the resiliency of the plastic filmrather than the materials contained within the cells. Thus, when apressure force is exerted against one of these cells, the substancewithin the cell will deform, uniformly distributing pressure against thecell walls and causing the plastic film to yield and absorb variousforces.

From the foregoing, it can be understood that this invention providesnew cushionings that offer many advantages over other materials nowavailable. The air cell constructions are ideal for disposablecushioning for packing merchandise for shipment and the elastomer-filledconstructions are especially well adapted to use in upholstery andfurniture. The following is by way of summarizing the principaladvantages of the cushioning materials that form the subject matter ofthis invention.

First, the disposable air cell cushioning offers large savings inshipping costs because of its superior ability to protect articles fromdangerous mechanical shock. Excelsior, crumpled or shredded paper andcellulose or cotton pads can all be permanently compressed or may settleand assume a smaller volume. However, each cell in plastic air cellcushioning acts like an air spring. After a cell is compressed, itrecovers completely, returning to its original volume in a predictablemanner. For these reasons, the predictable and superior performance ofone unit thickness of air cell cushioning may make it possible toreplace many units thickness of shredded paper or excelsior with anattendant reduction in weight and volume.

1. A method for the manufacture of lightweight, resilient closed-cellcushioning material comprising the sequential steps of: firstfabricating a preform structure by: continuously feeding two sheetscomprised of polymeric materials in superimposed relationship to eachother; forming cross seals by sealing the two sheets together alongspaced parallel lines extending substantially across the width of thesheets; forming a first marginal seal by sealing the two sheets to eachother along a line adjacent one end of the cross seals and parallel toand adjacent one side of the sheets; forming a second marginal seal bysealing the sheets to each other along a line spaced away from the otherend of the cross seals and parallel to and adjacent the other side ofthe sheets; and second, forming a sealed, inflated cellular structureby: introducing an inflation device between the second marginal seal andsaid other end of the cross seals; introducing gases under pressure bysuch inflation device into the unsealed spaces between the two sheets;continuously advancing the sheets with respect to the inflation devicein their elongated direction and slitting the second marginal seal; andforming a plurality of long seals by sealing the sheets together alongspaced parallel lines extending lengthwise of the sheets; whereby aplurality of closed cells containing gas under pressure is formed.
 2. Amethod according to claim 1 wherein the first and second marginal sealsare formed by initially manufacturing the elongated sheets in the formof a tube.
 3. A method according to claim 1 wherein the general shape ofeach cell is formed prior to inflation by embossing a pattern on thesuperimposed sheets.
 4. A method according to claim 1 including thesteps of winding the superimposed sheets onto a roll after the crossseals and first and second marginal seals have been formed and unwindingthe sheets from the roll prior to inflation and formation of theplurality of long seals.
 5. A method according to claim 3 wherein thepattern is embossed below the heat sealing temperatures of the film. 6.A method according to claim 1 wherein the resiliency of the cellularstructure is selectively altered by adjusting the pressure of the gasesunder pressure.